Driven axle

ABSTRACT

Proposed are free-wheel clutches (12) for a driven axle of an all-wheel-drive vehicle in which the degree to which the steered wheels (17, 18) are connected to the drive (4) depends on the steering angle. A snap-in catch in the clutches (12), as well as a passive locking device (59, 60), are switched over automatically by the output shafts (13, 14), the output shafts being connected to the steered wheels (17, 18) by double crossed joints (15, 16).

The invention concerns a driven axle having two output shafts coaxiallysupported in the axle housing, according to the invention.

BACKGROUND OF THE INVENTION

In a multi-track vehicle, if it travels around a curve, the wheels ofone axle run over curved paths of different diameters. Since theturnable-outer wheels cover a longer path than the turnable-innerwheels, they have different speeds if no slippage occurs between theground and the wheels. If the wheels are now driven together,precautions that permit suitably different speeds on the wheels withouttensions resulting between the wheels themselves and in the drive trainhave to be taken. Differentials or clutches, which distribute orinterrupt the drive to the wheels when cornering serve this purpose.

In EP-A 02 39 763 is described a driven axle for motor vehicles havingtwo free-wheel clutches both of which transmit to the synchronouslyrotating wheezes the power of an engine when traveling straight ahead.During a travel condition with varying ground adherence of the wheels,such as with one wheel upon ice and the other wheel on gripping solidsoil, the engine power, when the clutches are engaged, is transmitted toeach wheel in proportion to the adhesion limiting value so that optimaltraction values are obtained.

When cornering, a free-wheel clutch interrupts the drive to a wheel,especially to the turnable-outer wheel that runs more quickly during atraction operation. The free-wheel clutches, therefore, allow theseparation of the wheels or rigid transmission function depending on thetravel condition.

An expansion device contains a cylindrical bolt as a supporting elementand annular pistons provided with cams. The annular pistons arerotatable relative to the supporting element. The supporting elementfirmly connected with the housing of the free-wheel clutches rotatesduring stress cycle in the drive relative to the annular pistons andpressurizes the annular pistons in an axial direction. If in thetraction operation one of the wheels of the axle rotates more quicklythan the opposite wheel, its annular piston rotates in advance relativeto the supporting element in a drive direction so that the cams releasethemselves from the expansion device and the disengaged clutchinterrupts the connection between drive and quicker wheel. Separatelydisposed cams are provided on the annular pistons for forward andreverse travel.

The rotation in the direction of travel of the annular piston of theclutch which leads to the quicker wheel has to be limited in a mannersuch that its cam surface remains free for the opposite direction oftravel. Otherwise, the clutch could be engaged again by the cam surfacefor the opposite direction of travel and stresses result in the drivetrain.

In the above cited publication is described a clip which limits thetorsion clearance of the annular pistons. When cornering, the clip holdsthe annular piston leading to the turnable-outer quicker wheel in aneutral position free of axial force as long as the supporting elementwith the opposite annular piston holds its clutch engaged and connectsthe turnable-inner wheel with the drive. For a stress-free operation,two driving modes are provided:

cornering with a leading wheel and a driven wheel of an axle, and

straight-ahead travel.

Agricultural vehicles reach angles of lock of the steered wheel largerthan 50 degrees. The turnable-inner and turnable-outer steered wheels ofa front axle run from a specific steering angle larger than about 35degrees, for instance, to curved paths larger than the curved path ofthe central rear axle. If the motor vehicle is all-wheel driven, thewheels of the steered front axle in the presence of an adequatetransmission ratio between front and rear axles, are in a coastingoperation away from the specific steering angle.

If one of the steered wheels is in a coasting operation, as result ofits large path radius and remains, at the same time, rigidly connectedwith the drive, slippage occurs on this wheel and on the wheels still ina traction operation when there is an elevated load of the drive.

For stress-free operation of an all-wheel drive with a steering anglelarger than a specific steering angle of about 35 degrees, for instance,both steered wheels of a driven front axle should therefore run freelyin order to keep the drive free of additional stresses and to operatethe motor vehicle with improved efficiency.

SUMMARY OF THE INVENTION

The problem to be solved by this invention is to provide a driven axlehaving two free-wheel clutches which from the traction operationautomatically

makes possible the free wheeling of both the turnable-inner andturnable-outer wheels lock in case of angles of larger than a specificsteering angle of the steered wheels of an axle,

separates the quicker turnable-outer wheel from the drive and connectsthe turnable-inner wheel with the drive in case of angles of locksmaller than a specific steering angle of the steered wheels,

drives synchronously both wheels of an axle in case of straight-aheadtravel.

According to the invention, this is obtained by the fact that when usingthe axle as a steered axle of an all-wheel driven vehicle, the expansiondevice, starting from a specific steering angle, is held in the neutralposition with minimal expansion.

The annular pistons of the expansion device, from a specific steeringangle larger than about 15 degrees, for instance, are held in power-freeneutral position so that the clutches are disengaged. The annular pistonfor the turnable-outer wheel is held in the power-free neutral positionalready with small steering angles by the passive device and away from aspecific steering angle both annular pistons are additionally held by asnap-in catch.

The annular piston for the turnable-inner wheel, in the transition fromthe traction to the coasting operation, rotates automatically in adirection of the power-free neutral position where it is retained firmlyby the snap-in catch. This passive device is power free when thesteering angles are larger than a specific steering angle and only whenthe steering angle is again smaller than the specific steering angledoes the snap-in catch, dependent on the steering angle again disengageitself from the annular pistons and the passive device, which allows alimited torsion between the two annular pistons, determines theirtorsion.

According to the invention, the output shafts in a rigid axle areconnected with steered wheels via double-crossed joints.

The wheels are pivotally secured to the rigid axle housing. Withsteering angle of the wheels, the double-crossed joints produce an axialmovement of the output shafts. By virtue of this axial movement of theoutput shafts, dependent on the steering angle, a particularly precise,reliable and economic automatic actuation of the snap-in catch can beobtained. Away from a specific steering angle, the snap-in catch retainsthe expansion device in neutral position with minimal expansion.

According to the invention, the snap-in catch consists of two partshaving each shift teeth. The turnable-outer annular piston, already witha small steering angle, reaches the power-free neutral position and theturnable-inner annular piston does it only away from a large steeringangle. The steering angle produces on the turnable-inner wheel a swivelangle larger than on the turnable-outer wheel. The output shaftconnected with the inner-turnable wheel, already with a small steeringangle, presses the shift teeth of the snap-in catch in the annularpiston of the clutch toward the turnable-outer wheel so that the annularpiston is not held in the neutral position only by the passive deviceand can produce, from the expansion device, no engaging force on theclutch. Only from a specific steering angle of about 35 degrees, forinstance, does the output shaft connected with the turnable-outer wheelpress the shift teeth of the snap-in catch against the annular piston ofthe turnable-inner clutch so that the annular piston, when slipped alongin the direction of rotation by the inner-turnable wheel passing to thecoasting operation, is held by the snap-in catch in the passage throughthe neutral position. It is also obtained that the shift teeth actuatedby the turnable-outer wheel with the small steering angle releases theturnable-inner annular piston before the turnable-outer annular pistonwhen the steering angle diminishes, and the connection betweenturnable-inner wheel and drive is restored before the turnable-outerwheel is again connected with the drive.

According to the invention, it is obtained that the output shafts, forinstance, with a steering angle in parking, can press the shift teethwithout damage against the annular pistons when the shift teeth are nolonger aligned with a groove in the annular piston.

According to the invention, it is obtained that the annular pistonrotates without friction and consequently without hysteresis relative tothe supporting disc.

According to the invention, an easy opening of the clutch is madepossible by the rotatability of the external discs when the appertainingwheel should rotate more quickly than allowed by the drive.

According to the invention, the engagement of the shift teethautomatically disengages when the shift teeth are not pressed by theoutput shafts in grooves in the annular pistons.

According to the invention, the free-wheel clutches of the invention canalso be manually changed over to a neutral position so that the wheelsremain separated from the drive. The free-wheel clutches in one ofseveral driven axles can replace a shiftable clutch between the axles.If the wheels are in a traction or a coasting operation, there isproduced in a stress cycle a neutral position specified from outside.

The claims contain a logical combination of the solution features; othercombinations are easily possible for a skilled person within the scopeof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings are shown embodiments of the invention:

FIG. 1 a drive diagram of a 4-wheel motor vehicle,

FIG. 2 the free-wheel clutches according to the invention,

FIGS. 3A, 3B and 3C an operation diagram for supporting discs andannular pistons,

FIGS. 4/4a an active device for limiting the torsion of the lockingelements of the annular pistons,

FIG. 5 a cross section of the annular piston according to the invention,and

FIG. 6 a passive device for limiting the torsion of the half shells ofthe annular pistons.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1 are shown the geometric ratios in the embodiment of twodifferent steering angles for an all-wheel drive.

An internal combustion engine 1 drives, via a transmission 2, a pair ofspur gears 3 and a central input shaft 4, a steered, rigid front axle 5and a rigid rear axle 6, not steered. A bevel gear differential 7connects the wheels 8, 9 of the rear axle with the central input shaft 4via output shafts 10, 11. The front axle 5 contains free-wheel clutches12, according to the invention, which connects the output shafts 13, 14with the steered front wheels 17, 18 via double-crossed joints 15, 16.The thin broken line shows the front wheels with a small steering angleand the thick drawn line shows the front wheels with a large angle. Theperpendicular lines upon the planes of the turnable-inner wheels and theturnable-outer wheels 17, 18 intersect the line of the rear axle 6 at aninstantaneous center of rotation 19 or 20. Depending on the steeringangle, the instantaneous center of rotation changes its distance to thecenter of the bevel gear differential 7 of the not steered rear axle andto the front wheels. The distance of the instantaneous center ofrotation 19 from the turnable-outer wheel 18 and thus the path radiusthereof is to each steering angle always greater than the distance fromthe instantaneous center of rotation 19 to the center of the rear axle 6of the bevel gear differential 7. In case of a small steering angle, theradius path--the distance of the instantaneous center of rotation 19from the turnable inner wheel 17--is smaller than that from theinstantaneous center of rotation to the bevel gear differential 7 of therear axle 6. With a large steering angle, the path radius--the distanceof the instantaneous center of rotation 20 from the turnable-inner wheel17--is greater than that from the instantaneous center of rotation tothe bevel gear differential 7 of the rear axle 6. With a specificlimiting angle, which is dependent on the path width and the wheel baseand generally amounts to about 15 degrees, the distance of theinstantaneous center of rotation 19 from the turnable-inner front wheel17 is equal to that from the instantaneous center of rotation to thecenter of the bevel gear differential 7 of the rear axle 6. If theturnable-inner wheel 17 turns from a small steering angle to a steeringangle larger than the specific limiting angle, then, under an adequatereduction ratio between the front and rear axles, the turnable-innerwheel 17 changes from a traction to a coasting operation and converselyfrom a coasting to a traction operation when returning from the largerto the smaller steering angle.

If the front wheels 17, 18 are already in a coasting operation, forinstance, on a downhill run or when braking, no reversal from coastingto traction takes place when returning from the large to the smallsteering angle of the wheels 17, 18.

FIG. 2: A rigid axle housing consists of two axle bridges 21, 22 heldtogether by screws 23. A shaft 24 is driven by the shaft 4. The shaft 24is provided with a pinion 25 and rotatably supported with two taperedroller bearings 26, 27 in an axle drive housing 20. The axle drivehousing 20 can be integral part of the axle bridge 21.

The pinion 25 is in contact with a gearing of a crown gear 28, which isscrewed to a cover 29 of the housing 32 of the free-wheel clutches 12.The cylinder pins 30 act as protection against torsion between cover 29and the housing 32. The housing cover 29 is held by a tapered rollerbearing 31 in the axle bridge 22. The housing 32 of the free-wheelclutches 12 is supported in the axle bridge 21 via another taperedroller bearing 33. The housing cover 29 is screwed to the housing 32 ofthe free-wheel clutches 12. The output shaft 13 and the output shaft 14are rotatably supported, respectively, in the housing cover 29 and inthe housing 75.

The supporting disc 34 is non-torsionally held by means of studs 35 inthe housing 32 of the free-wheel clutch 12.

The free-wheel clutches 12 contain two disc sets 40, 41. The annularpistons 38, 39 are rotatable in relation to the supporting disc 34 ofthe free-wheel clutches 12 and abut against internal discs of the discclutches 40, 41. The internal discs are non-torsionally mounted oninternal disc carriers 42, 43 which are non-torsionally mounted with theoutput shafts 13, 14. External discs 77 of the disc clutches 40, 41 ofthe free-wheel clutches 12 are rotatably held in the housing 32 of thefree-wheel clutch 12 at an angle of about 30 degrees, for instance.

FIG. 3A: The supporting disc 34 contains cam surfaces R1, R2.Power-transmission elements 36, 37 such as rollers are situatedcoaxially with respect to both sides of the supporting disc 34.Power-transmission elements 36, 37 act upon the prestressed discclutches 40,41 via annular pistons 38, 39. The annular pistons 38, 39are provided with cam surfaces K1, K2 on the sine facing the supportingdisc 34.

FIG. 4, 4A, 5 show elements of an active shiftable device for limitingthe torsion of the annular pistons 38, 39 when the steering angle islarge. Locking elements 44, 45 contain, in grooves 65, fitting keys 46,47 which axially movably and non-torsionally are passed in the grooves48, 49 of the supporting disc 34. The locking elements 44, 45 abutagainst discs 50, 51 in the output shafts 13, 14. The discs 50, 51 arepressed by compression springs 52, 53, against guard rings (not shown)in the output shafts 13, 14. The locking elements 44, 45 have helicallycut shift teeth 56, 57 which are suited to engage in the grooves 54, 55of the annular pistons 38, 39.

For reasons of symmetry, the annular pistons 38, 39 each have twoopposite grooves 54, 55 so that the annular pistons are replaceable. Foroperation of the shift teeth 56, 57 only one groove 54 or 55,respectively, would be needed.

The engagement of the shift teeth 56, 57 in the grooves 54, 55automatically disengages itself when the locking elements 44, 45 areaxially power-free.

Radially projecting cylinder pins 58 are inserted on the periphery ofthe annular pistons 38, 39. Between the periphery of the annular pistons38, 39 and the housing 32 of the free-wheel clutch 12 there are adjustedmetal sheets 59, 60 which almost like half shells comprise the annularpistons 38, 39 and the supporting disc 34.

Disc carriers 76, in which external discs 77 are held with limitedtorsion, are integral with the housing 32.

FIG. 6: The metal sheets 59, 60 are the passive device for limiting thetorsion of the annular pistons 38, 39 when the steering angle is smalland medium. The metal sheets 59, 60 contain central recesses 61, 62 andtwo stops 63, 64 on each side. The studs 35 of the supporting disc 34extend through the central recesses 61, 62 into the housing 32 of thefree-wheel clutch 12 and center the metal plates 59, 60. The recesses61, 62 allow rotation of the metal sheets 59, 60 relative to thesupporting disc 34. Between both stops 63, 64 on each side of the metalsheets 59, 60, the cylinder pins 58 grip the annular pistons 38, 39. Thedistance from each other of the lateral stops 63, 64 is somewhat greaterthan the rotation which the annular pistons 38, 39 can cover relative tothe supporting disc 34 until the cams K1, K2, R1, R2 or thepower-transmission elements 36, 37 have closed the disc sets 40, 41 andfurther torsion is blocked.

Mode of Operation:

The speed of the input shaft 4 is transmitted by the shaft 24 to thesupporting disc 34 via the pinion 25, the crown gear 28 and the housing32 of the free-wheel clutches 12.

If the wheels 17, 18 of the axle 5 are neither in a traction nor in acoasting operation, the rollers 36, 37 and annular pistons 38, 39 arepower-free (FIG. 3a). The free-wheel clutches 12 (FIG. 1) aredisengaged.

Straight-ahead driving in traction operation:

FIG. 3B: In the stress cycle such as when starting off, the supportingdisc 34 moves relative to the power-transmission elements 36, 37 and theannular pistons 38, 39 which remain behind, as result of the slippageeffect of the internal discs in relation to the housing 32. Thepower-transmission elements 36, 37 move along on the ramps R1, R2 and,at the same time, are pressed away from and toward the annular pistons38, 39 from the central plane of the supporting disc 34. Thepower-transmission function of the supporting disc 34 on the free-wheelclutches 12 is reinforced by a complementary cam section K1, K2 on theannular piston surfaces facing the power-transmission elements 36, 37.The annular pistons 38, 39 press together the disc sets 40, 41. Thewheels 17, 18 are synchronously driven via the output shafts 13, 14. Thediscs 50, 51 of the output shafts 13, 14 are at the greatest possibledistance in an axial direction from the central plane of the supportingdisc 34. The locking elements 44, 45--passed by the fitting keys 46, 47into the grooves 65, 66--rotate with the supporting disc 34 and are freeof axial forces from the output shafts 13, 14 so that no engagement inthe grooves of the annular pistons 38, 39 occurs.

Cornering with small steering angle in traction operation:

FIG. 3C: The turnable-outer wheel 18 covers a wider path than all otherwheel 8, 9 and increases speed. The speed increase is further passedalong via the output shaft 14 and the disc set 40 thereof to the annularpiston 38 of the former. The annular piston 38 rotates away from theposition shown on FIG. 3B in a travel direction relative to thesupporting disc 34. The cams or profiled surface K1 of the annularpiston 38 becomes free from the axial components of thepower-transmission element 36. The external discs 77 are held in thehousing 32 rotatable by an angle of about 30° so that the internal discset 40 can release, without tension, the frictional connection betweenthe discs. The turnable-inner wheel 18 rotates free from the supportingdisc 34.

The cylinder pins 58 radially projecting on the periphery of theturnable-outer annular piston 38 abut against the stops 63 of the metalsheets 59, 60 in a travel direction.

Since the turnable-inner output shaft 13 remains in a traction operationwhen the steering angle is small and is driven further by the shaft 4,the cylinder pins 58 of the annular piston 39 hold the metal plates 59,60 on the stops 64 relative to the supporting disc 34 and the annularpiston 38 can rotate with the cylinder pins 58 in the travel directiononly by the angle between the stops 63 so that the torsion of theannular piston 38 in the travel direction relative to the supportingdisc 34 does not go far enough so that the profile cams R1, K1 againabut against the supporting disc 34 and annular piston 38 for theopposite direction of travel via the power-transmission element 36, andthe disc set 40 would again be axially pressurized and engaged. Theannular piston 38 remains in a power-free neutral position and the discset 40 disengaged.

From the steering angle of the wheels 17, 18 results, through thedouble-crossed joints 15, 16, for both output shafts 13, 14, axialmovement toward the supporting disc 34. Since the turnable-inner wheel17 has a larger steering angle than the turnable-outer wheel 18, theturnable-inner output shaft 13 moves more toward the supporting disc 34than the turnable-outer output shaft 14. The locking element 45 which isnon-torsionally but axially movably passed in the supporting disc 34 ispushed by the turnable-inner output shaft 13 to the turnable-outerannular piston 38. The turnable-outer annular piston 38 has alreadyreached its neutral position in which it is retained in the traveldirection by the stops 63 of the metal sheets 59, 60. The piston grooves54, 55 of the annular piston 38 are aligned in the neutral position withthe shift teeth 56 of the locking element 45 so that the displacement ofthe turnable-inner output shaft 13 can produce engagement of the shiftteeth 56 of the locking element 45 in the groove 54 or 55 in thepresence of a steering angle of 20°, for instance, and the annularpiston 38 is non-torsionally connected with the supporting disc 34.

The turnable-outer output shaft 14 has comparatively moved less towardthe supporting disc 34 and the locking element 44 is easily pressedagainst the turnable-inner annular piston 39 via the spring-prestresseddisc 50. Since the turnable-inner annular piston 39 is still in itstraction position, the piston grooves 54, 55 and the shift teeth 57 ofthe locking element are not aligned and the engagement of the shiftteeth 57 takes place.

Cornering with large steering angle in the traction operation:

If the steering angle of the turnable-inner wheel 17 of the front axleexceeds a certain limiting angle, which depends on the geometry of thechassis of the motor vehicle and generally amounts to about 35°, theturnable-inner wheel 17 also covers a wider path than the center of thebevel wheel differential 7 of the rear axle 6 and in the presence ofadequate ratio front/rear axle of 1:1, for instance, the wheel 17rotates quicker than predetermined by the drive 4. The increase in speedis transmitted via the output shaft 13 and the disc set 41, and theprofiled surface K2 of the annular piston 39 for the turnable-innerfree-wheel clutch 12 releases itself from the power-transmission element37 and the annular piston 39 rotates relative to the supporting disc 34likewise in the direction of travel. The cylinder pins 58 of the annularpiston 39 of the turnable-inner wheel 17 release themselves from thestops 64 of the metal sheets 59, 60 which can rotate together with thecylinder pins 58 in the travel direction.

The locking element 44 is pressed by the turnable-outer output shaft 14toward the annular piston 39.

If the annular piston 39, when rotating relative to the supporting disc34, reaches the neutral position, the shift teeth 57 of the lockingelement 44 overlaps with the grooves 54, 55 of the turnable-innerannular piston 39 and the locking element 44, prestressed by the spring52 of the turnable-outer output shaft 14, engages by its shift teeth 57in the groove 54 or 55 of the piston 39 and retains it in neutralposition in which the power-transmission elements 37 can transmit noaxial forces from the supporting disc 34 to the annular piston 39 andthe disc set 41 and thus the turnable-inner wheel 17 also remainsseparated from the input shaft 4.

The limitation of the torsion of the annular pistons 38, 39 has thusbeen transmitted from the passive device--half shells 59, 60--to theactive device--locking elements 44, 45--shiftable by the output shafts13, 14.

The position of the annular pistons 38, 39 relative to the supportingdisc 34 then corresponds to that of FIG. 3A.

Cornering with diminishing steering angle in traction operation:

The shift teeth 57 belonging to the locking element 44 and pressurizedby the turnable-outer double-crossed joint 16 via the output shaft 14undergoes, as a result of a small steering angle of the turnable-outerwheel 18, less axial displacement to the turnable-inner annular piston39 than the shift teeth 56 belonging to the locking element 45 andpressurized by the turnable-inner output shaft 13. If the steering angleis reset, the shift teeth 57 belonging to the locking element 44 andpressurized by the turnable-outer output shaft 14 releases first theannular piston 39 with the turnable-inner wheel 17 so that the discclutch 41 first can engage again and the turnable-inner wheel 17 isfirst connected again with the input shaft 4 for the traction operationwith small steering angles.

Coasting operation in straight-ahead travel:

Both annular pistons 38, 39 are, relative to the supporting disc 34, inthe angular position corresponding to the traction operation for theopposite direction of travel.

Coasting operation when cornering:

The turnable-outer wheel 18 drives the supporting disc 34 via theappertaining output shaft 14 and the free-wheel clutches 12. Theturnable-outer annular piston 39 cannot be released from the supportingdisc 34. The turnable-inner wheel 17 rotates slower and the appertainingannular piston 39 rotates relative to the supporting disc 34 contrary tothe direction of rotation until reaching the power-free neutral positionin which the turnable-inner annular piston 39 is held by the stops 64 ofthe metal sheets 59, 60. Independently of the steering angle, theturnable-outer wheel 18 remains in a coasting operation and theturnable-inner wheel in a power-free neutral position.

Disconnection of the axle drive:

A mechanical power-transmission device is provided for the manualcontrol of the free-wheel clutches 12 which is comprised of a leverextending outside the axle housing 21, a rotatable stud 68 witheccentric cams 69 and a stop 70 movable in the housing 32 of thefree-wheel clutches 12. The stop 70 acts against springs 72 on engagingelements 73 which can engage in grooves 74 on the periphery of theannular pistons 38, 39 and retain the latter in a power-free neutralposition so that the free-wheel clutches 12 remain disengaged. Themanual control can take place while the free-wheel clutches 12 are understress. During the stress cycle the free-wheel clutches change overautomatically.

We claim:
 1. A driven, rigid and steered axle having first and secondoutput shafts (13, 14) being coaxially supported by an axle housing (21,22); each of said first and second output shafts (13, 14) having one endthereof driving a wheel (17, 18), via a double-crossed joint (15, 16),and an opposite end thereof being rotatable with but axially movablyrelative to a pair of internal disc carriers (42, 43), each of said pairof internal disc carriers (42, 43) supporting a plurality of internaldiscs positioned to engage with a plurality of external discs beingsupported by a mating pair of external disc carriers, said pair ofexternal disc carriers being operatively connected with an input shaft(4) via a rotatable housing (32) to provide driving power to the wheels;said pair of internal disc carriers (42, 43), said pair of external disccarriers and said internal and external discs forming a pair of discsets (40, 41); an expansion device (34, 38, 39), having a supportingelement (34) firmly connected with said housing (32), being positionedbetween said pair of disc sets (40, 41); an annular piston (38 or 39)being positioned between said support element (34) and each of said pairof disc sets (40, 41); a first set of ramps (R1, R2) being provided onsaid supporting element (34) and extending in a direction of rotation,said first set of ramps (R1, R2) co-acting with a second set of ramps(K1, K2) provided on said annular pistons (38, 39); and a device (60)for allowing only limited torsion between said annular pistons (38,39);wherein each of said first and second output shafts (13, 14)actuates, by virtue of longitudinal displacement of the output shaft dueto a desired steering angle, a snap-in catch which, starting at adesired steering angle, maintains said expansion device in a neutralposition; and said snap-in catch comprises two locking elements (44, 45)which are rotate with but are axially movable with respect to saidsupporting element (34), each of said two locking elements (44, 45)respectively co-acts with one of said annular pistons (38 or 39) viashift teeth (56 or 57) carried by said locking element, and each of saidtwo locking elements (44, 45) is respectively actuated by one of saidfirst and second output shafts (13 or 14).
 2. The driven, rigid andsteered axle according to claim 1, wherein each of said first and secondoutput shafts (13, 14) actuates said locking element (44, 45) via aspring element (52, 53).
 3. The driven, rigid and steered axle accordingto claim 1, wherein said supporting element (34) comprises a supportingdisc and having rolling bodies (36, 37) situated between said first setof ramps on said supporting element (34) and said second set of ramps onsaid annular pistons (38, 39).
 4. The driven, rigid and steered axleaccording to claim 1, wherein said shift teeth (56, 57), of said lockingelements, (44, 45), and mating grooves (54, 55), formed in each of saidof annular pistons (38, 39), are helical in shape.
 5. The driven, rigidand steered axle according to claim 1, wherein said expansion device isconnected to a shifting device actuatable from an exterior of saiddriven, rigid and steered axle and, when said shifting device isactuated, said expansion device is maintained in a neutral position bysaid shifting device.